Please try to add a line
# -*- coding: utf-8 -*-
as the first line of your source file. I would like to see, if the character encoding is
set correctly. All text drawing is done by the QScintilla editor widget. However, it might
be initialized incorrectly, although I never saw such an issue on any of my systems
(Windows 7 and 10, various Linux and macOS).
In which version did it work? What was updated since then?

The screenshot indicates that you have a non-monospaced font configured. Try to change this
and let me know. If the characters are still wrong, this is a QScintilla issue. In that
case you should report it to the QScintilla mailing list because such an issue would be
outside my area of influence.